The use of digital cameras is becoming increasingly widespread. Captured digital images are typically stored in image files within the camera on some type of storage media, such as an internal flash memory, a removable hard drive, or on a removable flash memory card. One advantage over analog SLR cameras is that removable flash memory card. One advantage over analog SLR cameras is that digital cameras allow the user to play back the captured images on a liquid-crystal display (LCD).
Typically, the images are displayed sequentially based on an image number or the time and date that the images were captured. When the number of stored images is large, the user has difficulty finding particular images, and sequentially navigating among the images during the search can be tedious and slow. Therefore, digital cameras are being provided with a categorization feature in which a user may categorize the images for easier sorting.
For example, U.S. Pat. No. 5,633,678 issued to Parulski discloses a digital camera in which image category icons are displayed on the LCD for selection by the user so that the user may choose an appropriate category before taking a group of pictures. Examples of categories are Family, Work, Vacation, and Pets, for instance. After the user selects a particular category and captures an image, the category name is stored as a tag in the image file along with the image data.
By the time this patent issues, some cameras on the market will allow a user to display captured images on the camera based on their associated categories (e.g. the DC290 by Eastman Kodak Co. incorporating the Digita Operating Environment by FlashPoint Technology Inc.). To implement this sort function, the camera must build an inventory list in memory indicating which images belong to which categories. The camera builds this inventory list by opening each image and extracting the category tags.
Due to the time required to open and read the category tags from each image file, it is more efficient to build the inventory list each time the camera is turned-on, rather than each time the user requests a sort. But even building the inventory list at cameras start-up is less than optimal because the process may significantly increase the boot-up time of the camera. Even with faster processors and disk access time, this problem may grow worse in the future due to the advent of high-capacity storage media.
For example, now available on the market are tiny disk drives for digital cameras having 340 MB of storage space. Anticipated sizes within a year exceed 1 GB. This is enough storage capacity to store well over one thousand very large JPEG images. The time required to access that many images from a high-capacity storage media each time the camera is turned-on in order to build an inventory list would be a significant barrier to the marketability and usability of the camera.
Accordingly, what is needed is an improved method for managing images captured by a digital camera. The present invention addresses such a need.